If  n+1Cr+1:nCr:n−1Cr−1=11:6:3 then nr =

Given, n+1Cr+1 nCr=116 or n+1r+1×nCr nCr=116or 6n+6=11r+11 or 6n-11r=5 ----------(1)Also, nCr n−1Cr−1=63 or nr×n−1Cr−1 n−1Cr−1=63 or n=2r ----------(2)From (1) and (2),r = 5 and n= 10,.'. nr= 50